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Filtration
Canister Filter
An external sealed filter unit that pulls tank water through multiple media stages - the gold standard for medium-to-large freshwater tanks.
Price: Mid
For: Both $80-$400
📖 Overview
A canister filter sits below the tank, connected via intake and return hoses. Water passes through customizable media stacks - mechanical, chemical, biological - providing excellent water quality with modest flow noise. Popular for planted tanks and larger community setups.
🎯 Purpose
Combined mechanical (traps debris), biological (nitrifying bacteria colonization), and chemical (activated carbon, phosphate remover) filtration.
⚙️ How It Works
Pump draws water from the tank, pushes it through progressive media layers, and returns clean water via a spraybar or lily pipe. Fully sealed system means the water is under pressure and cannot spill.
⏰ When Needed
Tanks over 30 gallons. Planted tanks (for adjustable flow via spraybar). When silent operation matters. When you want customizable filter media choices.
✅ Pros
Highest water throughput per size. Very quiet operation. Enormous media capacity. Adjustable flow. Easy media customization.
❌ Cons
Setup complexity higher than HOB. Priming required. Leak potential if seals fail. Higher upfront cost.
🏷️ Top Brands
Eheim (German, industry gold standard), Fluval, OASE, SunSun (budget), Fx-series by Fluval for large tanks.
🧰 Maintenance
Rinse mechanical media in tank water monthly. Replace chemical media (carbon, phosphate) every 4-6 weeks. Bio-media rinses every 6-12 months. Check hoses and seals annually.